This is another of those threads that can never end. For what its worth, do this if you can. Use your spreadsheets' random number generator, or any other random number generator that uses a computer algorithm to generate "random" numbers. Generate a large number of random sets of x and y "data" between say 0 and 1, or any other finite reasonable range. Plot the x,y sets as points on a, say, a 2x2 grid, i.e., divide the field into 4 smaller square, subfields. You should see a uniform gray or speckled field, depending on how close the points are to each other. And if you count the number of points falling in each subfield the number should approach the same for each subfield as you plot more and more points.
I guarantee that you won't achieve this with any standard, simple computer random number generator. In fact, you will see a definite and repeated pattern in the plotted points! None of these simple, common, random number generating algorithms are any good for serious statistical work where you might be using monte carlo methods or the central limits theorem.
I haven't thought about how these algorithm's defects might show up in randomly generated price chart. But if you want to generate good pseudo-random numbers using a computer algorithm you'll need a more sophisticated algorithm, about which many papers have been written in the computer science literature, which see.
You can't get true random numbers from any computer algorithm. But good pseudo-random number algorithms do exist that will give you a nice uniform gray field in the above described "parking lot" test. And that is good enough. But the typical random number algorithms are mostly worthless for serious work.
(and laughing my ars off)
, should read: